The present invention relates to the use of a plant oil product as an agent for increasing the synthesis of skin lipids, especially the lipids of the epidermal skin barrier, in or for the preparation of a cosmetic, pharmaceutical or dermatological composition. The invention also relates to a method for cosmetic treatment with a cosmetic, pharmaceutical or dermatological composition for increasing the synthesis of skin lipids, especially the lipids of the epidermal skin barrier, and to the use of the plant product as a food additive.
The skin consists mainly of three layers: the epidermis, the dermis and the hypodermis.
The outermost layer, the epidermis, is characterized by organization into strata corresponding to a state of increasing differentiation of the keratinocytes, from the deepest region (stratum basale) to the outermost region (stratum corneum) within which anuclear elements (corneocytes) are included in a multilamellar extracellular lipid structure, the intercorneocytic cement, responsible for the skin's water barrier function and for protection against external attack.
The lamellar bodies, or Oddland bodies, secreted by the stratum granulosum, a layer intermediate between the stratum basale and the stratum corneum, contain cholesterol, phospholipids and glucosylceramides and also selective hydrolases. These enzymes convert phospholipids and glucosylceramides into free fatty acids and ceramides which form, with cholesterol and cholesteryl sulfate, the intercellular lamellar bilayers of the stratum corneum. Ceramides participate predominantly in the formation of the barrier formed by the stratum corneum and in regulating water flow by unifying the lamellae. A large reduction in the content of/and the type of ceramide is especially observed in atopic dermatitis (or atopic eczema) or in acne (ceramide 1) and in dry skin and pruritus in the elderly. Cholesteryl sulfate, via a specific sulfatase, is in equilibrium with cholesterol (leaflet-fluidizing agent). They play an important role in corneocyte cohesion and thus in skin desquamation, and also in skin comfort.
An impairment in this skin barrier caused by external attack (UV radiation, wind, cold, detergents, etc.), by the natural and inexorable phenomenon of aging and/or by pathological or nonpathological dysfunctions (sensitive, irritated or reactive skin) is manifested in a disruption in the epidermal homeostasis which it is desirable to able to prevent and/or treat both cosmetically and pharmaceutically and especially dermatologically.
For example, the article by Ruby Ghadially et al., “Decreased Epidermal Lipid Synthesis Accounts for Altered Barrier Function in Aged Mice”, The Journal of Investigate Dermatology, vol. 106, no. 5, May 1996, teaches that an impaired skin barrier and also an abnormal content of lipids in an aged mouse epidermis can be explained by an impaired synthesis of the epidermal lipids.